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Polyoxometalates (POMs) are transition metal complexes that exhibit a broad diversity of structures and properties rendering them promising for biological purposes.

The antibacterial activity of 29 different polyoxometalates (POMs) against Moraxella catarrhalis was investigated by determination of the minimum inhibitory concentration (MIC). The Preyssler type polyoxotungstate (POT) [NaP5W30O110]14− demonstrates the highest activity against M. catarrhalis (MIC = 1 μg/ml) among all tested POMs. Moreover, we show that the Dawson type based anions, [P2W18O62]6−, [(P2O7)Mo18O54]4−, [As2Mo18O62]6−, [H3P2W15V3O62]6−, and [AsW18O60]7− are selective on M. catarrhalis (MIC range of 2-8 μg/ml). Among the six tested Keggin type based POTs ([PW12O40]3−, [H2PCoW11O40]5−, [H2CoTiW11O40]6−, [SiW10O36]8−, [SbW9O33]9−, [AsW9O33]9−), only the mono-substituted [H2CoTiW11O40]6− showed MIC value comparable to those of the Dawson type group. Polyoxovanadates (POVs) and Anderson type POMs were inactive against M. catarrhalis within the tested concentration range (1-256 μg/ml). Four Dawson type POMs [P2W18O62]6−, [(P2O7)Mo18O54]4−, [As2Mo18O62]6−, [H3P2W15V3O62]6− and the Preyssler POT [NaP5W30O110]14− showed promising antibacterial activity against M. catarrhalis (MICs < 8 μg/ml) and were therefore tested against three additional bacteria, namely S. aureus, E. faecalis, and E. coli. The most potent antibacterial agent was [NaP5W30O110]14−, exhibiting the lowest MIC values of 16 μg/ml against S. aureus and 8 μg/ml against E. faecalis. The three most active compounds ([NaP5W30O110]14−, [P2W18O62]6−, and [H3P2W15V3O62]6−) show bacteriostatic effects in killing kinetics study against M. catarrhalis. We demonstrate, that POM activity is mainly depending on composition, shape, and size, but in the case of medium-size POTs (charge is more than −12 and number of addenda atoms is not being higher than 22) its activity correlates with the total net charge.

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Activated carbon (AC) has a relatively high efficiency for retaining TcO 4 -compared to other materials. AC is used on a vast scale in gas and water purification, metal extraction, medicine and many other applications. The TcO 4 -adsorption mechanism on AC is not fully known, however there are assumptions of ion-exchange reaction between AC surface and TcO 4 -anions. Adsorption and anion competitive investigation have shown that perchlorate anions have most influence on TcO 4 -adsorption. Adsorption properties depend on standard absolute molar enthalpies of hydration. Anion competitiveness was investigated with five samples that were prepared in different ways (this was already published in previous article), we used several anions Cl -, Br -, ClO 4 -, CH 3 COO -, NO 3 -, HCOO -and SO 4 2-at different concentrations. In general, the adsorption of TcO 4 -is influenced mostly by ClO 4 -, what is explained by its similar structure with TcO 4 -; however the co-existence of Fe 3? cations in the AC structure decreases TcO 4 -adsorption.

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